1. Field of the Invention
The invention relates to an all-solid-state secondary battery, a solid electrolyte composition and an electrode sheet for batteries used in the same, and manufacturing methods of an electrode sheet for batteries and an all-solid-state secondary battery.
2. Description of the Related Art
An electrolyte solution is used in lithium ion batteries which are currently widely used in many cases. There have been attempts to make all configuration materials be solid by substituting the electrolyte solution with a solid electrolyte. Above all, one of the advantages of the technique of using an inorganic solid electrolyte is reliability. In the electrolyte solution which is used in a lithium ion secondary battery, a combustible material such as a carbonate-based solvent is applied as a medium thereof. Various countermeasures are employed, but an additional countermeasure to be performed when a battery is overcharged is desired. An all-solid-state secondary battery formed of inorganic compounds that allow an electrolyte to be incombustible is regarded as solving means thereof. Another advantage is that an inorganic solid electrolyte exhibits higher ion conductivity than a polymer electrolyte.
Another advantage of the all-solid-state secondary battery is that a high energy density is suitably achieved by stacking electrodes. Specifically, the all-solid-state secondary battery can be a battery having a structure in which electrodes and electrolytes are directly arranged side by side to be serialized. At this point, a metal package that seals battery cells and copper wire or bus bars that connect battery cells can be omitted, and thus energy density of the battery can be greatly increased. It is advantageous that compatibility with a positive electrode material in which a potential can be enhanced to a high level is good.
According to the respective advantages as described above, the development of an all-solid-state secondary battery as a next-generation lithium ion secondary battery has been energetically advanced (see NEDO: New Energy and Industrial Technology Development Organization, Fuel Cells⋅Hydrogen Technology Development Field, Electricity Storage Technology Development Division “NEDO 2013 Roadmap for the Development of Secondary Battery Technology” (August 2013)). Meanwhile, an inorganic all-solid-state secondary battery has disadvantages caused by the fact that the electrolyte thereof is a hard solid. Examples thereof include increase of resistance on an interface between solid particles. In order to solve this problem, there are examples in which specific polymer compounds are used as binders. Specifically, in JP2013-008611A, a surfactant utilizing a polyoxyethelene chain is used. JP2011-134675A discloses the use of a hydrogenated butadiene copolymer. JP2002-042862A discloses a lithium ion secondary battery obtained by impregnating sulfolane in a gap between an active substance and an oxide-based inorganic solid electrolyte.